Apparatus and method for inhibiting melatonin synthesis in a horse

ABSTRACT

An apparatus for inhibiting melatonin synthesis in a horse comprises a blinker having an internal surface of which at least a part is diffusing. A source of light is positioned for direction into the horse&#39;s eye by the diffusing-surface. The light source and diffusing surface are configured such that the light directed into the horse&#39;s eye is blue.

CROSS-REFERENCE TO RELATED APPLICATIONS

This is a continuation of U.S. application Ser. No. 14/118,783, filed onNov. 19, 2013, which is the US national phase of InternationalApplication No. PCT/EP2012/059678, filed May 24, 2012, which claimspriority to Irish Application No. S2011/0245, filed May 27, 2011, theentire contents of each of which being fully incorporated herein byreference.

BACKGROUND

This invention relates to an apparatus and method for inhibitingmelatonin synthesis in a horse especially, but not necessarily, foradvancing the breeding season of non-pregnant mares.

Photoperiod signals are the primary regulators of reproduction inseasonally breeding animals. Melatonin is known as the hormone ofdarkness as its production by the pineal gland is confined to thenight-time hours; thus it acts as a decoder of seasonal day length inseasonally breeding animals. Light inhibits melatonin synthesis. As daysget longer in the spring, the duration of melatonin production isreduced and this lifts the inhibitory action of this hormone in a mare'sreproductive activity. Horses, as long-day breeders, normally foalbetween May and October. However, the universal birthday for many horsebreeds is January 1st. This necessitates a demand for early foals inorder to produce mature yearlings and two year old racehorses to meetindustry timelines for sales and racing schedules. Therefore advancedonset of the mare's breeding season is required.

Exposure of Thoroughbred breeding mares to lengthened hours of lightbeginning on December 1st and continuing for at least 8-10 weeks isstandard industry practice in order to advance the reproductively activeperiod of the mare's circa-annual reproductive cycle, thus permittingbreeding from February 15th, the official start of the Thoroughbredbreeding season. The maintenance of groups of mares indoors under lightsduring winter months is labour and energy intensive. Mares must remainindoors and require maintenance in terms of feeding, bedding and labourassociated with their upkeep during this time. This comes at a highcost. The estimated upkeep for a mare during this time is

20/day (feed, bedding, labour, light) and if maintained for 10 weekstotals can involve costs of about

1400.

For this reason, pregnant mares are not usually maintained under lightsto advance the perceived breeding season.

Multiple studies have investigated the influence of time of breeding ongestation length and found that the earlier in the year that the mare isbred, the longer the gestation period. Mares bred between January andMay have on average a 10-day longer gestation period than mares bredduring their natural breeding season. This has important implicationsfor the industry as the mare has an approximate 11 month gestationperiod (330 days). Provided that she foals on time, stud managers haveone month to ensure she becomes pregnant again to prevent a laterfoaling date the subsequent year. If the gestation length of earlyfoaling mares could be shortened it would provide crucial extra time topermit a successful timely conception for the subsequent pregnancy. Astudy (Hodge et al, 1982) has shown that the administration ofartificial light to pregnant mares beginning December 1st significantlyshortens the gestational length by 10 days. It is assumed that this isnot commonly practiced in the industry due to the high cost associatedwith keeping all pregnant as well as non-pregnant mares under artificiallighting.

A more recent unpublished study has shown that not only is thegestational period lengthened in early foaling mares, but that the birthweight of foals born in January and February is significantly lower thanfor a foal born later in the year. The Hodge (1982) study showed atendency towards higher birth weights in mares provided with artificiallighting. It is therefore desirable to reduce gestation length andincrease foal birth weight in pregnant mares.

Currently, the only known solution is to leave the stable lighting onover housed mares. The literature (Palmer and Driancourt, 1981) statesthat a 100 Watt light bulb in a 12 ft×12 ft stall (enough light to reada newspaper) burning for 16 hrs a day provides sufficient light for thispurpose. As stated, this is costly.

U.S. Pat. No. 4,858,609 discloses a bright light mask system for shininga high intensity light into a subject's eyes at pre-selected timeperiods to modify circadian rhythms. The system includes a mask adaptedto be worn by the subject (possibly a race horse) for covering thesubject's eyes regardless of body position. The mask includes at leastone light admitting aperture that is transparent to light energy. Alight source is coupled to the aperture for generating and directinglight into the subject's eyes. At least 2000 lux of light having awavelength in the range of 500 to 600 nanometers (nm) is delivered toeach of the subject's eyes. A controller dictates the intensity of thelight generated and the periods during which the light is on.

It is an object of the present invention to provide a morecost-effective apparatus and method for inhibiting melatonin synthesisin a horse.

SUMMARY OF THE INVENTION

According to the invention there is provided an apparatus for inhibitingmelatonin synthesis in a horse, comprising a blinker having an internalsurface of which at least a part is diffusing, and a source of lightpositioned for direction into the horse's eye via the diffusing surface,the light source and diffusing surface being configured such that thelight directed into the horse's eye is blue.

It will be understood that the internal surface of the blinker is thesurface of the blinker which in use faces the horse's eye and isusually, but not necessarily, concave or approximately concave.

In a preferred embodiment the light source emits blue light and thediffusing surface does not significantly filter the blue light.

Preferably the blue light has a peak wavelength of from 440 to 490 nm,preferably 459 to 484 nm, and most preferably 468 nm.

Preferably the light source has an intensity of from 10 to 100 lux, mostpreferably 10 to 5 50 lux.

The light source may comprise at least one LED.

Preferably the diffusing surface of the blinker is diffusivelyreflective.

Advantageously the light source is shielded to substantially avoiddirect illumination of the horse's eye.

The blinker may be mounted in a mask adapted for fitting to a horse'shead.

Preferably the mask contains only a single said blinker for directingblue light into only a single eye of the horse.

The apparatus preferably includes an automatic timer for turning thelight source on and off at selected times.

The invention further provides a method of inhibiting melatoninsynthesis in a horse, comprising directing diffused blue light into thehorse's eye for at least one selected period of time.

Preferably the blue light is directed into only a single one of thehorse's eyes at any given time.

The method may be used for the purpose of advancing the breeding seasonof non-pregnant mares, shortening the gestation length in early foalingmares, and/or increasing the birth weight of foals born in the earlymonths of the year.

The method may also be used for the purpose of mitigating the effects ofjet lag in a horse.

The invention is based upon the recognition that the photic pathwaysinvolved in circadian, neuroendocrine and neurobehavioural responses inthe retina are independent of those that convert light signals to neuralsignals for the visual system. Melanopsin is the photopigment mediatingthese non-visual responses in conjunction with rod and cone cells and isfound in a novel set of photoreceptors called intrinsicallyphotosensitive retinal ganglion cells (ipRGCs). The action spectra forthese photoreceptors show peak sensitivities in the short-wavelengthregion of the visible spectrum and studies conducted in mice and humansindicate a peak sensitivity range between 459 nm and 484 nm. Since, forhorses, we are most interested in the circadian and neuroendocrinesignals that reach the SCN (the part of the brain regulating biologicalrhythms), we chose a suitable wavelength range that has shown to beeffective in other species and likely to be effective in horses, as wehave shown. The light chosen is not light for vision, but light tostimulate the SCN.

The advantages of the invention are that mobile timed lighting can beprovided to mares while they remain in their natural outdoor pastureenvironment. This means that the mares do not need to be housed indoorswith the associated bedding, feed, electricity and labour costs. Notonly will this facilitate an advanced reproductive breeding season fornon-pregnant mares, but it will now permit highly cost effective meansof reducing gestation length of pregnant mares and increasing foal birthweights.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the invention will now be described, by way of example,with reference to the accompanying drawings, in which:

FIG. 1 is a schematic view of a mask for fitting to a horse's head, themask incorporating a blinker according to a first illustrated embodimentof the present invention.

FIG. 2 is an enlarged view of the blinker in the mask of FIG. 1.

FIG. 3 shows a housing containing battery-powered circuitry forswitching the LED on and off at selected times.

FIGS. 4 and 5 are perspective views of a blinker according to a secondillustrated embodiment of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring to the drawings, a horse's face mask, FIG. 1, comprises afabric base 10, approximately 600 mm wide, having ear openings 12, eyeopenings 14 and fasteners 16 for fastening the mask behind the horse'sneck. To that extent the face mask is a conventional design.

In accordance with a first illustrated embodiment of the invention, oneof the eye openings 14 is fitted with a blinker 18, FIG. 2, the blinkercomprising a rigid cup 20 having a diffusively reflective internalconcave surface 22. The cup 20 is fixed to a semi-rigid annular base 24,the latter being fitted around the eye opening 14. The internal diameterof the annular base 24 is about 104 mm, and the height of the cup 20 isabout 53 mm. An LED 26 emitting blue light is mounted on the blinker atthe junction of the cup and base. The LED 26 is positioned to shine bluelight on the reflective surface 22, from where it is diffused into thehorse's cornea. The reflecting surface is white so that it does notsignificantly filter the blue light. The LED 26 is shielded from directillumination of the horse's eye.

The construction of the mask such that the horse is exposed to diffuselight, that provides much less distraction than a light directly pointedat the eye. We have found that the behaviour of horses remained normaland they continued to feed or rest during the time they were exposed tothe blue light.

The blinker 18 with blue LED 26 and reflecting surface 22 is fitted toonly one of the two eye openings 14, since melatonin can be inhibited byadministration of light to a single eye. This is important since theblue light administered to a single eye will not impede the naturalbehaviour of horses maintained outdoors at night, whereas lightadministered to both eyes might impede vision and movement. Horses thatare blind in a single eye can move and behave normally. The other eyeopening 14 would normally be left open, but if desired a conventionalblinker could be fitted. It would also be possible to swap the LEDblinker 18 from one eye opening 14 to the other at various times, tobalance the effect on the horse, as long as the blue light is onlyadministered to one eye at any given time.

The fabric base 10 of the mask includes a pocket 28 for containing apower supply 30, FIG. 3, for the LED 26. The power supply is connectedto the LED by leads 32 and has a battery compartment 34 for areplaceable and/or rechargeable battery, and an on/off switch 36. It ispossible to operate the device manually, by switching the power supplyon and off at various times, but it is preferred that the power supplyinclude an automatic timer to turn the LED on and off at pre-selectedtimes. Such a timer may be a manually settable timer or, morepreferably, a programmable electronic circuit which can be programmed bycomputer, e.g. via a USB port. In this embodiment the power supply 30has approximate dimensions 96 mm×60 mm×26 mm.

In variations of the first embodiment, diffuse light is directed towardsthe horse's eye without being reflected from a surface. In one example(not shown), an LED is provided with a diffusing lens surface and thisis located towards the centre of the blinker and directed towards thehorse's eye. The diffusing surface of the LED can be provided by forexample, covering a lens surface in a generally transparent glue andcuring the glue; and/or simply sanding the surface of the lens. This candiffuse light from the LED sufficiently not to be a distraction to thehorse, but to nonetheless achieve the treatment goals outlined below.

A second illustrated embodiment of the invention is shown in FIGS. 4 and5. Here a blinker 18′ again comprises a rigid or semi-rigid cup 20′ ofsimilar dimensions to the blinker 18 of the first embodiment. In thiscase, the cup 20′ includes an integrally formed annular base 24′, thelatter being fitted a round a harness eye opening 14. In thisembodiment, a number of stitching holes 25 are defined in the base 24′and these can be used to sew the cup to the material of the harness, aportion 10 of which is shown.

A pair of windows 40 are defined in the cup 20′ and it has been foundthat these can enable a horse to see through the blinker 18′ withoutaffecting the performance of the device. Similarly, one or more suchwindows could be defined in the blinker 18 of the first embodiment.

The internal surface of the cup 20′ can be provided with a reflectiveand/or diffusing surface finish.

A recess 42 is defined at the centre of the cup 20′ and is approximately30 mm in diameter. A circular PCB (not shown) including a number,preferably 6, LEDS is located in the recess 42 with the LEDS beingdirected towards the opening 14. The LEDS are preferably disposed aroundthe periphery of the PCB to provide a larger light emitting area than inthe first embodiment and so make the blinker less susceptible to beingblocked by dirt. The PCB is connected via wires (not shown) running fromthe recess externally of the blinker 18′ to the power supply 30 shown inFIG. 3. The PCB can either include the necessary control electronics orthe LEDs can be controlled from electronics located near the powersupply.

In the second embodiment, an inner shell 22′ is fitted within the cup20′. The shell 22′ is formed of a translucent diffusive material, forexample, silicone. Thus, the shell 22′ serves to retain the PCB inposition; diffuse light emitted from the LEDs; and to seal the PCB fromingress of moisture.

In the present embodiments, the LED 26 emits blue light with a peakwavelength at 468 nm and we have found that 10-50 lux of such lightdirected at a single eye can inhibit the production of the hormonemelatonin in the horse to daytime levels. This contrasts with naturaldaylight which provides anywhere from 1000 to 10,000 lux of light,depending on cloud cover. Using the embodiments, therefore, melatoninlevels in the horse can be successfully inhibited using as little as10-50 lux of blue light to a single eye.

We have found that the invention may be implemented using blue light ingeneral, but preferably having a peak wavelength from 440 to 490 nm, andmost preferably having a peak wavelength from 459 to 484 nm, aspreviously discussed. The lux levels of the blue light are very lowcompared to natural daylight, and preferably 10 to 100 lux and mostpreferably 10 to 50 lux. The blue light source may comprise more thanone LED (or other lamp type) and if so the lux levels specified aboverefer to the combined output of all lamps.

The following regime of on/off blue light periods is recommended foradvancing the breeding season of non-pregnant mares. The blue light isadministered each day from about 1st December for at least 6 weeks, mostpreferably 6-8 weeks. The blue light is turned on before dusk andremains on so that the mare receives a combined total of at least about16 hours of natural daylight and blue light each day (overlappingperiods of daylight and blue light do not count double in the total).

Preliminary results have shown that use of the above described treatmentregime can be at least as effective as maintaining animals indoors underbarn lighting to advance the breeding season of mares.

In addition to advancing the breeding season of mares, the invention canbe used to mitigate the effects of jet lag in a horse. Jet lag isconsidered one of society's most prevalent disorders and is aconsequence of a misalignment of internal rhythms of physiology and anew light/dark cycle following abrupt changes in time zones (jettravel). Minimising disruption of circadian rhythms (24 h rhythms) isbecoming an important a rea of research in order to minimise the risk ofjet lag in athletes and thus sub-optimal performance (Reilly et al,2005). We have shown in a recently published paper (Martin et al, 2010)that horses have circadian rhythms in activity and gene expression inskeletal muscle. In particular, key genes related to performance undergoa 24-h profile that is regulated by the light/dark cycle. Equineathletes are exposed to the same time zone displacements as their humancounterparts due to the global nature of the industry and the ease oftransporting these animals to international competition. Thus, jet lagis an issue for horses. Jet lag can be overcome if timed lighting thatgradually adjusts to the light dark cycle at the destination isadministered prior to travel. The present invention could facilitatethis task without interrupting the management of the horses or theirtraining regime.

The following regime of on/off blue light periods is recommended formitigating the effects of jet lag on a horse: Dusk and dawn should bedelayed or advanced, respectively, in selected daily increments (10 min,30 min, 60 min) using light provided by the light mask, for a durationof time such that the animal is synchronized to the destinationlight/dark cycle prior to travel. Generally the light cycle should beadvanced by a maximum of one hour per day when flying east and delayedby one hour per day when flying west. The number of days of lighttherapy should correspond roughly to the number of time zones crossed.

In the foregoing embodiments, the face mask is implemented as a fullhood, but in the simplest case it could be configured as a simple maskjust covering one eye.

In a variant of the first embodiment, the LED 26 could be a white lightemitting LED, and the internal surface 22 of the cup 20 could befabricated as a diffusively reflecting blue filter, either by providinga white diffusively reflecting surface with a separate transparentfilter in front of it, or by making the internal surface itself of ablue diffusively reflecting material. In a similar variant of the secondembodiment, the LEDs could also emit white light and the inner shell 22′of the cup 20′ could act as a filter providing diffuse blue light.

Further variants of the above described embodiments, may include anautomatic ambient light sensor that, in combination with the timer, canmodulate the turn-on and/or turn-off times for maximum efficiency.

Equally, rather than simply switching the LEDs on and off at thebeginning and end of illumination periods, illumination could bemodulated in brightness so that for example, intensity could fade in andout over a period of 30 minutes.

Further variations of the above embodiments incorporate materials, whichduring or following illumination at certain wavelengths (or when heatedor shaken) emit light at particular wavelengths.

Thus, the cup 20, 20′ and/or shell 22′ can be fabricated to include sucha material, or mixture of materials, which emit visible light in therange to which the horse is sensitive as outlined above. Such materials,due to ambient conditions, emitting some constant or time varying amountof suitable light can supplement or replace the light from the LED lightsource, so cost effectively improving battery performance.

One mechanism for producing such light is photoluminescence. A materialexhibiting

photoluminescence soaks up energy from the environment (e.g. the lightfrom the sun) and then slowly releases the energy stored over somespecific range of wavelengths after dark.

Photoluminescence could be employed in embodiments of the invention inat least two ways:

-   -   Doping the inner diffusing shell 22′ with this material; or    -   Covering the internal surface of the cup 20,20′ a nd/or inner        shell 22′ with photo luminescent paint.

A suitable blue photo luminescent material, with a half-life of 3-6hours i.e. the time it takes for the light emitted to drop to half itsinitial value would burn/emit light most brightly for a few hours afterbeing illuminated by ambient light. Thus in a first phase of operationthis material could provide the primary source of illumination. Anambient light sensor could then detect the level falling off, and thenramp up the LED source as appropriate. Again, the benefit of using thesematerials is that battery life would be prolonged, i.e., a smallerbattery could be used, or more functions requiring electrical powerincorporated in the device.

Indeed in further embodiments of the present invention, kineticallygenerated power can be harnessed from the horse's movement to power thelight source and/or control electronics.

It is also observed that use of present invention advances the sheddingof a horse's winter coat. This reduces the costs associated with eithermanually and/or accelerating shedding via housing under artificiallight.

The invention is not limited to the embodiment(s) described herein butcan be amended or modified without departing from the scope of thepresent invention.

1. A light-based method of inducing physiological change, the methodcomprising the step of shining light from an artificial blue lightsource into just one eye of a female horse or other animal, each day forat least 6 weeks, causing a substantial suppression of melatoninproduction sufficient to induce physiological change, the physiologicalchange being advancing a breeding season of the horse or other animal,wherein the treatment regime is at least as effective as maintaining thehorse or other animal indoors under barn lighting to advance thebreeding season of the horse or other animal.
 2. The method of claim 1,in which the light source provides only blue light with a peakwavelength in the range 440 nm-490 nm.
 3. The method of claim 1, inwhich the light source provides only blue light with a peak wavelengthin the range 459 nm-484 nm.
 4. The method of claim 1, in which the lightsource provides blue light with an intensity of under 100 lux at thejust one eye of the female horse or other animal.
 5. The method ofpreceding claim 4, in which the light source provides blue light with anintensity of between 10-50 lux at the just one eye of the female horseor other animal.
 6. The method of claim 1, in which the light source isturned on before dusk.
 7. The method of claim 1, including the step ofproviding to the horse or other animal a combined total of natural andartificial light for at least approximately 16 hours during each 24 hourperiod.
 8. The method of claim 1, comprising the step of keeping thehorse or other animal outdoors whilst the low intensity light is shonein just one eye of the horse or other animal.
 9. The method of claim 1,comprising the step of keeping the horse or other animal in outsidepasture for at least 6 weeks in the two or three months at the start ofthe animal's breeding season.
 10. The method of claim 1, in which theartificial light source is used from approximately 1 December for aperiod of approximately 6 weeks.
 11. The method of claim 1, in which theartificial light source produces only low intensity blue light.
 12. Adevice for inducing physiological change, the device comprising a maskfittable to a head of a female horse, or a mask fittable to a head ofanother animal, and including an artificial blue light source, thedevice configured to shine light from the artificial blue light sourceinto just one eye of a female horse or other animal, each day for atleast 6 weeks, causing a substantial suppression of melatonin productionsufficient to induce physiological change, the physiological changebeing advancing a breeding season of the horse or other animal, whereinthe device is at least as effective as indoor barn lighting to advancethe breeding season of the female horse or other animal.
 13. The deviceof claim 12, in which the light source provides only blue light with apeak wavelength in the range 440 nm-490 nm.
 14. The device of claim 13,in which the light source provides only blue light with a peakwavelength in the range 459 nm-484 nm
 15. The device of claim 12, inwhich the light source provides blue light with intensity of under 100lux at the just one eye of the female horse or other animal.
 16. Thedevice of claim 15 in which the light source provides blue light withintensity of between 10-50 lux at the just one eye of the female horseor other animal.
 17. The device of claim 12, which includes a controlthat is capable of turning on the device such that when turned on, thecontrol leaves the device on so that the animal receives a combinedtotal of natural and low intensity blue light for approximately 16 hoursduring each 24 hour period.
 18. The device of claim 12, which isweatherproof so that the device is capable of being used on an animalthat is kept outdoors whilst the low intensity light is shone in thejust one eye of the horse or other animal.
 19. The device of claim 12,when used on an animal that is kept in outside pasture for at least 6weeks in the two or three months preceding the start of the animal'sbreeding season.
 20. The device of claim 12, the device including aharness including a blinker that covers the eye into which theartificial light is shone.
 21. The device of claim 20 in which theharness fits around the head of the animal and is designed to beweatherproof so that it is operable outdoors over a period of at least 6weeks.
 22. The device of claim 12 in which the artificial light sourceproduces only low intensity blue light.
 23. The device of claim 12, inwhich the artificial blue light source includes a white light LED.
 24. Asystem including a control and a device, the device comprising a maskfittable to a head of a female horse's head or to a head of anotheranimal, and including an artificial blue light source, wherein thedevice is for inducing physiological change, the device configured toshine light from the artificial blue light source into just one eye of afemale horse or other animal, each day for at least 6 weeks, causing asubstantial suppression of melatonin production sufficient to inducephysiological change, the physiological change being advancing abreeding season of the horse or other animal, wherein the device is atleast as effective as indoor barn lighting to advance the breedingseason of the female horse or other animal, and wherein the control isconnectable to the device such that when turned on, the control leavesthe device on so that the animal receives a combined total of naturaland artificial light for approximately 16 hours during each 24 hourperiod.